NS_GET_OWNER_UID(2const)                              NS_GET_OWNER_UID(2const)

NAME
       NS_GET_OWNER_UID - discovering the owner of a user namespace

SYNOPSIS
       #include <linux/nsfs.h>  /* Definition of NS_GET_OWNER_UID */
       #include <sys/ioctl.h>

       int ioctl(int fd, NS_GET_OWNER_UID, uid_t *uid);

DESCRIPTION
       The NS_GET_OWNER_UID operation can be used to discover the owner user
       ID of a user namespace (i.e., the effective user ID of the process that
       created the user namespace).

       fd refers to a /proc/pid/ns/user file.

       The owner user ID is returned in the uid_t pointed to by the third
       argument.

RETURN VALUE
       On success, 0 is returned.  On error, -1 is returned, and errno is set
       to indicate the error.

ERRORS
       EINVAL fd does not refer to a user namespace.

STANDARDS
       Linux.

HISTORY
       Linux 4.11.

SEE ALSO
       ioctl(2), ioctl_nsfs(2)

Linux man-pages 6.19              2026-02-08          NS_GET_OWNER_UID(2const)